Automated sensing can be employed to produce a large amount of data with little or no human intervention. Automated sensing can also be employed in environments where humans cannot readily work, for example inside nuclear reactors, in space or along the wings of commercial passenger aircraft. An automated sensing unit may be termed a sensor, wherein a sensor may be capable of sensing a physical property. A sensor may further be capable of communicating its sensing data periodically or as a continuous sensor data stream.
Sensor networks comprise a plurality of sensors, or sensor nodes, which may be connected to each other and/or a central node by means of wireless or wired communication links. A sensor network may be employed to sense temperature, pressure or other physical properties. For example, sensors may be installed in a combustion pressure vessel to monitor the temperature thereof and help produce an integrated understanding of operating conditions of the pressure vessel. Data from the sensor network may be visualized on a computer monitor in a control room, for example, where a shape of the pressure vessel may be coloured according to current temperature variations.
Continuous data from a plurality of sensors may facilitate understanding complex phenomena that may otherwise be difficult to grasp. For example in fusion energy research a large number of sensors can simultaneously measure properties of a plasma, such as temperature, pressure and magnetic field strength, which can be fed into a neural network to effect real-time management of plasma parameters to control plasma instabilities. In some cases, sensors may be dispersed over a large geographic area to provide information remotely, for example in a border region between sovereign countries where sensors may measure movement or detect people from their body heat with infrared detectors.
Sensors comprised in sensor networks may be powered by batteries, or alternatively by direct or indirect connection to a stable power supply. Where batteries are used, replacing the batteries becomes necessary to prevent sensor data from ceasing when the batteries run out. Power requirements of sensors may vary, in certain applications sensors can be designed to consume very little power by minituarization and employing low-power communication.
In some sensor networks, packet-switched communications are used to relay sensor data from sensors. In networks with relatively few sensors, circuit-switched communications may be employed. An example of the latter are closed-circuit television monitoring systems, where a limited number of cameras produce circuit-switched television monitoring data which may be observed in monitors in a local or remote guard post.